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KentuckyFC writes "Quantum cryptography uses the quantum properties of photons to guarantee perfect secrecy. But one of its lesser known limitations is that it only works if Alice and Bob are perfectly aligned so that they can carry out well-defined polarization measurements on the photons as they arrive. Physicists say that Alice and Bob must share the same reference frame. That's OK if Alice and Bob are in their own ground-based labs, but it's a problem in many other applications, such as ground-to-satellite communications or even in chip-to-chip communications, because it's hard to keep chips still over distances of the order of the wavelength of light. Now a group of UK physicists have developed a way of doing quantum cryptography without sharing a reference frame. The trick is to use entangled triplets of photons, so-called qutrits, rather than entangled pairs. This solves the problem by embedding it in an extra abstract dimension, which is independent of space. So, as long as both Alice and Bob know the way in which all these abstract dimensions are related, the third provides a reference against which measurements of the other two can be made. That allows Alice and Bob to make any measurements they need without having to agree ahead of time on a frame of reference. That could be an important advance enabling the widespread use of quantum cryptography."

Yeah, that's just what I was going to say. He stole my idea!
Don't panic. Find comfort in the fact that there's a universe in which a bear brutally sodomized then killed him before he was able to push the Submit button.

Two, it kills a LOT of cats! You get the code right, and BAM! dead cat.

I always suspected that all this "entangling photon pairs" and "quantum encryption channel" stuff was just a bunch of scientists jerking off, but I didn't think they were actually euphemisms for spanking it!

Its not about hate, its about recognising that animals have feelings too. If you ever had a pet you would know this of course.. Also, I just saw this comment [slashdot.org] about copyright law and the UK Pirate Party which applies to PETA just as much. You can be sure that they won't get anywhere near what they are asking for but they know that and want you to consider that already you are sitting in an unethical position. They want to and need to rub your face in it be

Applying the standard naming conventions would result in qutits. I much prefer qutits.

And the scientific community would be rather better off choosing names that let us focus on the furtherance of humanity's knowledge of the inner workings of the universe than opening the door for juvenile jokes.

Applying the standard naming conventions would result in qutits. I much prefer qutits.

And the scientific community would be rather better off choosing names that let us focus on the furtherance of humanity's knowledge of the inner workings of the universe than opening the door for juvenile jokes.

the same abbreviational logic that turned "binary digit" into "bit" turned "trinary digit" into "tit." This nomenclatural error set computing back nearly three hundred years, and two entire generations of promising computer scientists were lost trying to keep abreast of bad puns.

Would this system still allow alice/bob to know if someone's evesdropped? What's the difference between a hostile evesdropper and just some other part of the infrastructure for getting data from alice to bob? Without that, quantum cryptography is just another encryption system, and there are nothing wrong with the current ones. Right? (It would arouse me if replies to this post started simply "Wrong.")

I think this is engineering, not theory. Theory was the original idea of using entanglement for cryptography. Now they're applying the technology to make it practical, and that's engineering. They're adding a bit of steel or another entanglement to make it more usable. If nobody has built this device yet, it's theoretical engineering.

The Billard Ball [wikipedia.org] is the difference between theory and engineering. The Theoretician tells the Engineer it can't be done. The Engineer does it anyway. And the Theoretician "accidentally" kills the Engineer with the resulting invention.

You've discovered the Quantum Theory of Engineering: If it practical enough to produce, Business School Product will screw it up into being impractical to produce. The tricky part is that if Business School Product is practical enough to produce, then Business School Product becomes impractical to produce. When this happens, a fixed point is reached and all the world's business schools go out of business because it is then recognized no one in their right mind would go into the business of building a busine

No, in all your years of/. have you never followed one of those developer != engineer rants? For this to be considered engineering, at the very least the failure of the process should put people in mortal danger. Since People != Cats, we can assume this is not engineering. This is priobably more akin to some sort of quantom crafting than engineering.

Quantum physics does not have a car analogy. Cars cant be mixed up and then split so each part has a bit of the other, and not just physically. if one car starts, it means its parts in both entangled sets start and the moment you go and look witch of the cars you have it becomes one or another, instantly causing the other entangled car thingy to become the car you didn't get.
Also, fu Eve.

Quantum physics does not have a car analogy. Cars cant be mixed up and then split so each part has a bit of the other, and not just physically. if one car starts, it means its parts in both entangled sets start and the moment you go and look witch of the cars you have it becomes one or another, instantly causing the other entangled car thingy to become the car you didn't get. Also, fu Eve.

Alice wants to get out of her car and into Bob's car. In laboratory conditions both cars are perfectly still so it's easy. Out on the freeway travelling at high speeds it's a recipe for disaster.

But these clever engineers have come up with a wonderful design for a semi-trailer that both cars can sit on while being driven down the freeway. Now Alice and get out of her car and into Bob's car for that secret rendezvous. In the middle of the freeway.

Well, you have to consider that FLAG wasn't confident enough about the capabilities of their car's artificially intelligent on-board computers to recognize its driver to not require a hidden fingerprint scanner underneath its door handles as an access control.

But these clever engineers have come up with a wonderful design for a semi-trailer that both cars can sit on while being driven down the freeway. Now Alice and get out of her car and into Bob's car for that secret rendezvous. In the middle of the freeway.

The quantum entanglement measurements will only work with two entangled photons when the velocities and accelerations of the two parties involved are the same. But if you're doing it with two objects with different motion, say a person on the ground and a satellite orbiting the earth, it won't. The satellite is in free fall and, according to general relativity, not in an accele

there's no such thing as a straight-line orbit.
Find an orbit where you pass through one of the Lagrange points. While you are in the Lagrange points, you are moving in a straight line, because all accelerations cancel each other out there.

No car analogy, but I think I summarize it a little simpler (though I am no expert).In Quantum Cryptography it's possible to detect the presence of an eavesdropper. The eavesdropper, by the act of listening changes the transmission of the signal and is provably unable to put it right again. This is possible because of some physics mumbo-jumbo and is highly sensitive to the distances between the people involved.As best I can make out, this research used more physics mumbo-jumbo to encode the distances betw

They are working on developing a communication technology that would allow one absolute proof that nobody is listening in. (if anyone tried to listen in, it would always be detectable.) You don't think that there are vast applications for such a technology?

Polarization has a nasty habit of rotating when it travels through optical (telecom) fiber. To make matters worse, the degree of rotation depends on temperature and physical strain and can change quite rapidly. Of course, entangling three photons is much harder than entangling two.

Apparently you missed the whole reason why quantum cryptography is radically different:
It is IMPOSSIBLE to duplicate the quantum key or the quantum message exactly.
So Michaels qubits are different from the one Bob sent AND there are ways for Alice to find out that they are different, so she knows eavesdropping has occurred.
It's a bit like making a copy of a letter
- that self destructs when it is copied or read
- that looks different depending on the light you use to scan it/read it (for example rgb(1

Apparently you missed the whole reason why quantum cryptography is radically different:It is IMPOSSIBLE to duplicate the quantum key or the quantum message exactly.So Michaels qubits are different from the one Bob sent AND there are ways for Alice to find out that they are different, so she knows eavesdropping has occurred.

It's a bit like making a copy of a letter- that self destructs when it is copied or read- that looks different depending on the light you use to scan it/read it (

Nothing. What frame reference independence actually means is that they are encoding a reference frame in the particles themselves, so that you don't have to worry about external alignment. It does nothing about the communication channel, that does not exist through an events horizon.